A high frequency heating apparatus having high frequency wave generating means for outputting a high frequency wave into a heating chamber containing a heated object has rapidly been spread as an electronic range which is a heating cooking apparatus of a food material or the like since the heated object in the heating chamber can be heated in a short period of time and efficiently.
However, there is an inconvenience that heating is limited only to heating by high frequency heating and the apparatus cannot deal with various ways of cooking.
Hence, there is proposed a high frequency heating apparatus capable of executing oven heating by adding an electric heater for generating heat in a heating chamber and in recent years, there is proposed a high frequency heating apparatus having a steam generating function capable of executing also heating cooking by high temperature steam by adding a steam supply mechanism for supplying heating steam into a heating chamber (for example, JP-A-54-115448).
The steam supply mechanism in the high frequency heating apparatus of the background art is constructed by a constitution of including a water storing tank detachably mounted to an apparatus main body, a fed water receiving bowl (evaporating portion) mounted into the heating chamber, heating means for evaporating water on the fed water receiving bowl (evaporating portion) by heating the fed water receiving bowl (evaporating portion) and exclusive pump means for supplying water in the water storing tank to the fed water receiving bowl (evaporating portion) and by mounting the pump means, there poses a problem that the constitution is complicated and large-sized.
Further, according to the steam supply mechanism of the background art using the exclusive pump means, in order to control an amount of supplying steam into the heating chamber, simultaneously with a temperature control of the heating means, also a control of a supply amount by the pump means is needed and there also poses a problem that a control processing necessary for controlling the supply amount of steam is complicated.
Further, water stored in the water storing tank is delivered to the fed water receiving bowl (evaporating portion) by the exclusive pump means, during the time period, water is delivered without being subjected to preparatory heating or the like (also for avoiding a trouble of the pump from being brought about by hot water) and therefore, a temperature of water supplied to the fed water receiving bowl (evaporating portion) is low, and there also poses a problem that a long period of time is taken during a time period until generating steam by heating the fed water receiving bowl (evaporating portion) by the heating means.
On the other hand, it is also possible to supply water to the fed water receiving bowl by heating a transport tube for supplying water from the water storing tank to the fed water receiving bowl (evaporating portion) and boiling water at inside thereof In this case, it is necessary to control an amount of heating the transport tube.
That is, when supply of heat to the transport tube is large, supply of heat to the evaporating portion becomes deficient and water is stored at the evaporating portion. Further, steam having a low temperature is generated, or an amount of steaming becomes insufficient. Further, although in order to evaporate water without leaving a water component in the evaporating portion, it is necessary to increase a heat capacity provided to the evaporating portion or operate heating means after stopping to supply water, when the heat capacity of the evaporating portion is increased, a rise time period until generating steam is prolonged and in the latter case, a method of detecting a temperature is needed.
On the other hand, when an amount of heat supplied to the transport tube is small, a failure in transportation is brought about. Further, when the failure in transportation is brought about, there is not a load of consuming the amount of heat generated by the heating means and therefore, the temperature of the heating means per se is elevated by self heat generation. In accordance with elevation of the temperature, the amount of heat supplied to a side of the transport tube is increased, and when the amount exceeds a threshold, water is transported while producing local boiling. As a result, the heating means returns to a predetermined temperature by supplying a load of consuming the heat amount to the evaporating portion. When the temperature is lowered to the predetermined temperature, the failure in transportation is brought about again. By repeating the phenomena, there also poses a problem of promoting adherence of scale in accordance with rapid local boiling in the transport tube to bring about clogging of the transport tube.